A laser processing apparatus which is provided with a laser oscillator, a support table and an optical system is known. In laser processing apparatus, the laser oscillator oscillates a laser beam, the support table supports a work, and the optical system guides the laser beam to a processing point of the work. It is also known that defects of an processed product can be detected by detecting processing accuracy in a laser processing using such a laser processing apparatus.
A product inspection can be performed off-line by extracting part of the processed products from a processing line of a laser processing and observing shapes etc. of the part of the extracted processed products with a measuring instrument provided separately.
A processing apparatus which enables an inspection on-line is also known. In the processing apparatus, optical paths of a laser beam for processing and a visible light for measurement are arranged on the same axis so that an optical system for processing and an optical system for measurement are combined. In this case, measurement accuracy may lower in the optical system for measurement due to variation of a distance from a lens for laser processing to a work.